1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device capable of easily identifying alignment errors of a polarizer plate attached to a LCD substrate, and a manufacturing method thereof.
2. Description of the Background Art
Liquid crystal display devices have been widely used as display devices for OA equipment such as personal computers or word processors and audiovisual equipment such as TV sets, video movies, and car navigations because the display devices have many advantages such as lightness, compactness and low power consumption.
In a process to manufacture the liquid crystal display device, predetermined alignment marks are used as an alignment tool to form various patterns, to cut a plurality of liquid crystal display panels from a LCD mother substrate and to attach films or plates such as polarizer plates the liquid crystal display device.
For example, Japanese laid open patent application No. 2007-121688 discloses a technique to form alignment marks at corners of a mother substrate. Under this technique, alignment marks are discarded after cutting the mother substrate into unit substrates. In this technique, the alignment mark is crossed shape and formed simultaneously with a black matrix using the same material as the black matrix in a case where the alignment mark is formed on a color filter side substrate. On the other hand, Japanese laid open patent application No. 2005-266284 discloses a technique to display an alignment mark to attach a polarizer plate at inside of a display area so as to overlap with an alignment mark formed on the polarizer plate. Further, the Japanese laid open patent application discloses an alignment mark formed outside of the display area in the liquid crystal display panel in advance.